Current regulator



y 29, 1952 J. PETERSON 2,605,457

' CURRENT REGULATOR Filed Aug. 8, 1951 Fig.1.

Inventor: Justin Peterson,

His Attorney.

Patented July 29, 1952 Justin Peterson, Swampscott, Mass., assig-nor to General Electric Company,-a-corporation of New Yorkv Application August s, 1951, Serial No. 240,901

, s My invention relates to current regulators, and

more particularly to static constant current regulators of the series resonant type.

In series lighting circuit, it is frequently necessary in order to accommodate a large number of lamps, that the output voltage of a constant current regulator supplying the circuit be of rather large value. This is best'provide'd by im ductive coupling'of theout put terminals with the resonant regulator circuit, as by transformer coupling between the resonant circuit and the output terminals. In such acircuit, it is of course evident that the constant current output may be adjusted by means of adjustable taps on the transformer secondaryor output winding. Such an arrangement is shown in the Patent 2,195,969 Miner. Where the output voltage is quite high, however, the high voltage switching means necessary to provide such an arrangement are large and expensive. I

It is therefore a'principal object'of my invention to provide new and novel switching means for adjusting the output'current in a constant current resonant regulator of the static type.

It is a more specific object of my invention to provide a constant current regulator of the static resonant type for series lighting circuits, such as airport runway lighting, wherein low voltage switching means are provided for adjusting the output current to control the brightness of the lamps.

In carrying out the invention in one form, I provide upon a single 'magnetizable core having a plurality of legs, a plurality of elements of a constant current regulating system. Upon one leg I provide an input auto-transformer winding, and upon another leg I provide output transformer windings of the isolated secondary winding type, the primary winding of which is arranged to be connected through a capacitor across selectable points on the input auto-transformer. The core is provided with a leakage flux path, and the reactance of the capacitor is made equal to the sum of the leakage reactance of the output transformer primary winding and the equivalent leakage reactance of the input winding referred to in the output transformer primary winding. By thus combining all the inductive elements of the regulator upon a common core, the weight and expense of the equipment are maintained at a minimum, and in addition, by switching the connection of the capacitor to the output of the relatively low voltage auto-transformer to control the magnitude of constant current output, the

4 Claims. (01. zza-z) cost, size, and weight of the switching apparatus arereduced.

My invention will be more fully understood and its various objects and advantages further appreciated by referring now to the following detailed specification taken in conjunction with the accompanying drawing, in which Fig. 1 is a schematic-circuit diagram of a resonant constant current regulating apparatus embodying my invention, and Fig. 2 is a simplified circuit diagram of the same apparatus showing the fundamental relationship of the various windings.

Referring now to the drawing, I have there illustrated a resonant regulating apparatus for supplying substantially constant current to a variable impedance load I froma substantially constant voltage source 2 of alternating electric current supply. The load l is shown for simplicity as a variable resistor, and such resistor may, for example, be taken to represent a series light- 'in load wherein the number of lamps in the series circuit is variable.

The regulating apparatus itself is mounted upon a single three-legged magnetizable core 3 having two integral legs 4 and 5 and a third high reluctance shunt leg 6 provided with an air gap 6a. No windings are mounted upon the high reluctance shunt leg 6, but this leg serves as a leakage path for magnetic flux in the legs 4 and -5'. Upon the integral core leg 4, there is mounted an input auto-transformer winding I having a pair of input terminals 8 and 9 which are adapted to be'connected to theconstant voltage supply sourc 2. The input terminal 9 is connected through a selector switch H! to any one of a. plurality of taps on the auto-transformer winding 1 in order to adjust the regulator for variations in the voltage of the source 2. Upon the other integral core leg 5, there is disposed a winding ll, one end of which is connected to the input terminal 8 and the other end of which is connected to one terminal of a capacitor l2. The leakage reactance of the winding ll together with the equivalent leakage reactance of the winding 1 referred to the winding 1 I are selected to be substantially equal to the reactance of the capacitor l2, and the winding II and capacitor I2 are arranged to be connected in series circuit relation across selectable portions of the input autotransformer winding 1. For this latter .purpose, there is provided a selector switch I 3 arranged to connect the other terminal of the capacitor l2 to any desired one of a plurality of taps l3a on the output side of the auto-transformer winding 1.

Upon the core leg 5 there is also disposed another winding M in inductive relation with the winding H, and constitutingwith the winding ll an isolated secondary winding of an output transformer, of which the winding ll forms the primary winding. The ends of the winding M are connected to a pair of output terminals l5 which are thus fixedly inductively coupled to the winding H and are adapted to be connected to the variable impedance load I.

It will now be readily understood by those skilled in the art that by reasons of the series resonant nature of the circuit including the capacitor l2 and the winding leakage reactances, the current in the output transformer secondary winding M for any predetermined setting of the selector switches l0 and I3 is substantially constant and is independent of the impedance of the load I below the saturation limit of the core leg 6. The particular desired value of this constant current may be adjusted by changing the position of the selector switch l3, thereby to vary the input voltage applied to the resonant circuit ll, I2.

While I have shown only a preferred embodiment of my invention by way of illustration, many modifications will occur to those skilled in the art, and I therefore wish to have it understood that I intend in the appended claims to cover all such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A current regulator for supplying substantially constant current of selectable value to a variable impedance load from a substantially constant voltage source of alternating electric current supply comprising a magnetizable core forming a closed magnetic circuit and a shunt flux path thereacross, an auto-transformer winding mounted on said core to embrace said closed magnetic circuit and having input terminals adapted to be connected to said constant voltage supply source, a second winding mounted on said core to embrace said closed magnetic circuit, a capacitor having a reactance substantially equal to sum of the leakage reactances of both said windings referred to said second winding, switching means for connecting said second winding and capacitor in series circuit relation across selectable portions of said autotransformer winding, and output terminals fixedly coupled to said second winding.

2. A current regulator for supplying substantially constant current of selectable value to a variable impedance load from a substantially constant voltage source of alternating electric current supply comprising a magnetizable core forming a closed magnetic circuit and a shunt flux path thereacross, an auto-transformer winding mounted on said core to embrace said closed magnetic circuit and having input terminals adapted to be connected to said constant voltage supply source, a second winding mounted on said core in inductive relation with and connected at one end to said auto-transformer winding, a capacitor having one terminal connected to the other end of said second winding and having a reactance substantially equal to the sum of the leakage reactance of both said windings referred to said second winding, switching means for connecting the other terminal of said capacitor to selectable spaced apart points on said auto-transformer winding, and output terminals fixedly coupled to said second winding. 3. A current regulator for supplying substantially constant current of selectable value to a variable impedance load from a substantially constant voltage source of alternating electric current supply comprising a magnetizable core forming a closed magnetic circuit and a shunt flux path thereacross, an auto-transformer winding mounted on said core to embrace said closed magnetic circuit and having input terminals adapted to be connected to said constant voltage supply source, a second winding mounted on said core to embrace said closed magnetic circuit, a capacitor having a reactance substantially equal to the sum of both the leakage reactances of said windings referred to said second windin switching means for connecting said second winding and capacitor in series circuit relation across selectable portions of said auto-transformer winding, and output terminals fixedly inductively coupled to said second winding.

4. A current regulator for supplying substantially constant current of selectable value to a variable impedance load from a substantially constant voltage source of alternating electric current supply comprising a three-legged magnetizable core having an air gap in one leg thereof, an auto-transformer winding mounted on a second leg of said core and having input terminals adapted to be connected to said constant voltage supply source, a second winding mounted on a third leg of said core in inductive relation with and connected at one end to said autotransformer winding, a capacitor having one terminal connected to the other end of said second winding and having a reactance substantially equal to the sum of the leakage reactances of both said windings referred to said second winding, switching means for connecting the other terminal of said capacitor to selectable spaced apart points on said auto-transformer winding, an output winding on the third core leg in inductive relation to said second winding, and output terminals fixedly connected to said output winding.

JUSTIN PETERSON.

No references cited. 

